Chapter 18 Surgical Haemostasis Flashcards
What are the three main principles used to augment haemostasis?
- Reduction in blood flow to affected area
- Topical haemostatic agents
- Antifibrinolytics
What are the three main principles used to augment haemostasis and list examples of each.
-
Reduction in blood flow to affected area
- Topical vasoconstrictors
- Hypotension/hypothermia/reduced perfusion
- Distant control of blood flow
-
Topical haemostatic agents
- Mechanical
- Active
- Haemostatic sealants
-
Antifibrinolytics
- Serine protease inhibitor
- Lysine analogues
What are the three main principles used to augment haemostasis, list broad examples of each, and specific examples
-
Reduction in blood flow to affected area
- Topical vasoconstrictors
- Epinephrine 0.01 - 1 mg/kg
- Hypotension/hypothermia/reduced perfusion
- Distant control of blood flow
- Clamps or tourniquets
- Topical vasoconstrictors
-
Topical haemostatic agents
- Mechanical
- Collagen
- Gelatin
- Cellulose
- Polysaccharide spheres
- Bone wax
- Ostene
- Active
- Thrombin
- Alginates
- Haemostatic sealants
- Fibrin
- Synthetic sealants
- Mechanical
-
Antifibrinolytics
- Serine protease inhibitor
- Aprotinin
- Lysine analogues
- TXA
- Epsilon-aminocaproic acid
- Serine protease inhibitor
List vessels that can be permanently ligated (11 in total)
How long can the following vessels be ligated for?
Descending thoracic aorta
Pringle manouvre
Hepatic artery
Splenic artery and vein
Renal artery and vein
Abdominal aorta
5 - 10 mins: Descending thoracic aorta
10 - 15 mins: Pringle manouvre
30 mins: Hepatic artery
15 - 20 mins: Splenic artery and vein
30 mins: Renal artery and vein
30 mins: Abdominal aorta
How long can descending thoracic aorta be occluded for?
5 - 10 mins
How long can the pringle manouver be performed for
10 - 15 mins
How long can the hepatic artery be occluded for?
30 mins
How long can the renal artery and vein be occluded for
30 mins
How long can abdominal aorta be occluded for
30 mins
How long can splenic artery and vein be occluded for?
15 - 20 mins
What is an esmarch tourniquet
Esmarch tourniquets are usually made of a broad elastic material and are applied tightly from distal to proximal, thus exsanguinating the limb. The Esmarch bandage is then secured tightly at the proximal aspect of the limb, preventing blood from flowing into the limb during surgery; thus, the limb is not only prevented from bleeding but also has had the blood removed
What is the recommended pressure of a tourniquet?
100 mmHg above patients systolic BP
What is the formula for pressure exerted by a tourniquet
P is pressure (Pa)
T is bandage tension (N)
R is the radius of curvature of the limb (m)
W is bandage width (m).
What is recommended time limit for tourniquet
1.5 - 2 hours
(at which point muscle ATP stores are depleted)
Name 2 contraindications to (limb) exsanguination
Infection or neoplasia
What are the three categories of haemostatic agent
- Mechanical
- Active
- Haemostatic sealant
List 5 possible complications of haemostatic agents
- Exothermic reaction
- Volumetric swelling
- Immunogenic reaction
- FB reaction
- Inhibition of normal tissue healing
List 2 contraindications to use of haemostatic agents
- Auto-transfusion (can pass through 40 um filter!) planned
- Intravascularly
How do mechanical haemostatic agents work?
- Mechanical barrier –> tamponade
- Scaffold for clot formation
In vitro, which mechanical haemostatic agent performed best?
Microfibrillar collagen > collagen sponge > gelatin > cellulose
What is source of gelatin?
Porcine
(“Gelofoam”)
What mechanical and active haemostatic agents are often combined
Thrombin + gelatin
(N.B. Thrombin cant be combined with cellulose because cellulose –> acidic environment which inactivated thrombin)
In terms of action, how does gelatin differ from cellolose
Gelatin doesnt cause platelet aggregation
What type of collagen is used as haemostatic agent
Bovine type 2 collagen
(–> mechanical action but also enhances platelet aggregation)
What is surgical
Oxidized regenerated cellulose
Aside from haemostasis, name an additional feature of cellulose
Acidifying –> bactericidal
What is a noteable feature of polysaccharide spheres?
500% volume expansion
Rapidly metabolised by endogenous amylases (24 - 48 hours)
What is bone wax made of?
Beeswax + paraffin or isopropyl palmitate
List 3 potential adverse effects of bonewax
- Inhibits bone healing
- Infection
- Embolization
- FB reaction
(not dog/cat studies though)
What is Ostene
Mechanical haemostatic agent
Blend of water-soluble sythetic alkaline oxide co-polymers
Advantages:
- No effect on bone healing
- Little FB reaction
- Less infection risk
- Adheres better to wet bone surfaces
What factor is thrombin
Factor 2
How does thrombin work as an active haemostatic agent
Utilizes normal clotting cascade, actively converting fibrinogen to fibrin
i.e. ineffective of consumptive coagulopathy
What is source of thrombin
What is a concern re repeated use of thrombin
Bovine, human or recombinant
Development of antibodies (which might cross-react with endogenous thrombin)
What are alginates derived from
How do alginates –> haemostasis
Seaweed
Contact with saline/body fluids –> Calcium ion release –> activation of clotting cascade
NAme an N.B. re alginates
Not for use in cavities –> FB reaction.
Need to be rinsed off with saline irrigation - used over wounds
What is benefit of a fibrin haemostatic sealant
Independent of patients clotting ability
What is Duraseal
A synthetic haemostatic sealant
–> 50% volume increase
What is main concern re synthetic sealants?
Swelling
Coseal –> 400%
Duraseal –> 50%
As fibrinolytics, how do lysine analogues compare with serine protease inhibitor?
Lysine analogues more potent
How do anti-fibronolytics work?
Inhibit plasmin- or plasminogen mediated fibrinolysis
i.e. not effective if depletion of clotting factors or coagulopathy
How is TXA excreted?
Unchanged in urine
What is haemostatic effects of Desmopressin?
–> vWF and VIII release from endothelial cells
What is ethamsylate
“salt” used as an oral or iv haemostatic agent
(falls under miscellaneous haemostatic products)
Interestingly may work synergistically with desmopressin and improves pancreatic blood flow in necrotizing pancreatitis + might be anti-inflammatory
NAme 2 haemostatic polymers/minerals
- Zeolite (exothermic) = crystalline mineral –> water adsorbtion + activates platelets + releases calcium (–> clotting cascade activation)
- Chitosan: High SA – gel like clot. Independent of clottinh factors and still forms in presence of heparin/warfarin
